Anticipating emerging preventive and interventional modalities for HIV infection, collaborating investigators from three American universities Case Western Reserve University (CWRU), Columbia University (CU), and University of California, San Francisco (UCSF) with counterparts from Makerere University (MU) and Uganda Ministry of Health (MOH) have joined forces to capitalize on the complementary nature of their research activities to form a Consortium for Cohort Studies in Uganda (CCSU). Specific Aims are: 1. To develop, maintain and expand three longitudinal cohorts: i. Maternal/infant cohort initiated by CWRU and the Departments of Obstetrics/Gynecology and Pediatrics at MU. ii. Rakai District general population cohort established by CU and the MOH. iii. STD clinic cohort including longitudinal follow-up of discordant couples, developed by UCSF and MU. 2. To assess biological and behavioral co-factors that are associated with HIV transmission and progression in the three cohorts, with special emphasis on STDs as risk factors. 3. To establish and test core activities that will assure uniform acquisition and management of demographic, behavioral and clinical data, and of biological specimens, so as to strengthen research design, enhance the quality and comparability of data, and maximize efficiency of data analysis and laboratory support. 4. To establish a research team and appropriate data instruments to assess the feasibility and acceptability of vaccines in HIV-uninfected and infected Ugandans; and to conduct a vaccine trials to validate behavioral data concerning vaccine acceptability, test consent and related procedures, assess the feasibility of conducting adult vaccine trials, and develop and field-test the infrastructure required to conduct large-scale adult vaccine trials. 5. Based on the above activities, to train Ugandan counterparts in all key aspects of vaccine trials. 6. To obtain specimens from recently-infected individuals within these geographically dispersed cohorts, for genetic and antigenic characterization of prevalent isolates of HIV-1.